1. Field of the Invention
The present invention relates generally to a semiconductor device and a method of manufacturing the semiconductor device, and is applicable, for example, to an FeRAM (Ferro-electric Random Access Memory).
2. Description of the Related Art
In recent years, attention has been paid to an FeRAM using a ferroelectric capacitor as one of nonvolatile semiconductor memories.
The ferroelectric memory device adopts a so-called COP (Capacitor On Plug) capacitor structure, from the standpoint of an area penalty, wherein electric connection between a capacitor electrode and a source/drain of a transistor is realized by a conductive contact plug (see Jpn. Pat. Appln. KOKAI Publication No. 2004-6593, for instance). In addition, from the standpoint of adhesion of the capacitor electrode, an adhesive film of a metal such as Ti (titanium) is, in usual cases, provided at an interface of the capacitor electrode.
However, with an increasing demand for finer microfabrication, there is a need to decrease the thickness of an Ir (Iridium) film of the capacitor electrode, which also functions as an oxygen diffusion prevention film. If a recovery anneal step in an oxidizing atmosphere for recovering damage in a capacitor forming step, or another heat treatment step in an oxidizing atmosphere is performed with the thickness of the capacitor electrode being thin, the capacitor electrode would fail to sufficiently suppress diffusion of oxygen, resulting in leakage of a slight amount of oxygen from the capacitor electrode.
The oxygen that leaks out may oxidize the adhesive film, and an oxidized adhesive film (TiOx film) may continuously form between the contact plug and the capacitor electrode. Consequently, direct contact would be lost between the capacitor electrode and the contact plug, and the conductivity between the capacitor electrode and the contact plug is degraded.